JPH06189186A - Method and device for judging back light and method and device for correcting back light in video camera - Google Patents

Abstract

PURPOSE:To obtain video pictures provided with the appropriate distribution of brightness by judging back light in a video camera and not using a stroboscope when the back light is judged. CONSTITUTION:Photographing picture data obtained by preliminary image picking up are tentatively stored in a frame memory 19. The range of the brightness indicated by the picture data is divided into the total of four levels, darker two levels A and B and brighter two levels C and D and the histogram of the brightness in the respective levels is obtained. When the frequency of the brightness in a relatively brighter section within the darker two levels is larger than the ones of the other sections, back light photographing is judged in a back light judging circuit 20. Back light correction is performed for the picture data obtained by main photographing by an amplifying/knee-processing circuit 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight determination method and device for a video camera (including a movie video camera, a still video camera, a movie / still video camera, etc.) and a backlight correction method and device.

[0002]

BACKGROUND ART A video camera has a built-in solid-state electronic image pickup device such as a CCD that generates a video signal representing a picked-up subject image. Since the dynamic range of the solid-state electronic image pickup device is relatively narrow, it is difficult to take both images with proper exposure when the difference in brightness between the bright part and the dark part included in the visual field is large. For example, if the exposure is adjusted to the dark part, the bright part will appear white, and if the exposure is adjusted to the bright part, the dark part will be blackened.

For example, in the case where the background is very bright and the main subject in the center is dark, as in the case of shooting under backlight, when shooting in a room with a window and the main object is in the room and the outside scenery is reflected through the window, etc. is there. When shooting such scenes, if the exposure is adjusted so that the main subject (often a person) is properly exposed, the amount of incident light exceeds the dynamic range of the solid-state electronic image sensor for bright background areas. Is saturated, the bright background is not photographed and the image in that part simply becomes white (overexposure).

Therefore, in general, a device is devised to increase the brightness of the main subject by strobe light emission (daytime synchrocross flash photography). However, a stroboscopic device is required for daytime synchro stroboscopic photography, the camera becomes large and its operation is troublesome. In addition, in the case where the dark part is in the distance, or when it extends from a short-distance place to a long distance, the daytime synchro-stroboscopic photography is not always effective.

[0005]

DISCLOSURE OF THE INVENTION The present invention enables a video camera to determine whether or not there is backlight, and to obtain a video image with proper brightness without using a strobe when it is determined to be backlight. The purpose is to do.

In order to achieve the above object, the present invention provides:
Provided are a backlight determination method and apparatus for a video camera, and a backlight correction method and apparatus.

According to the method for determining backlight of a video camera according to the present invention, the range of brightness represented by an image signal obtained by image pickup is at least two steps in the bright side and 2 in the dark side with the average brightness as a boundary. When the appearance frequency of brightness in each step is calculated by dividing into at least 4 steps in total, and the appearance frequency in the relatively bright section of the two steps divided into the darker is higher than the appearance frequency in other sections It is determined to be backlight photography.

A backlight judging device according to the present invention comprises an image pickup means for outputting an image signal representing an object, an image storage means for storing an image signal output from the image pickup means, and a brightness of an image stored in the image storage means. The range of
The average brightness is used as a boundary to classify into at least 2 stages for the bright side and 2 stages for the dark side, totaling at least 4 stages,
A backlight determining unit that determines the appearance frequency of the brightness in each stage and determines the backlight shooting when the appearance frequency in the relatively bright segment of the two segments divided into the darker segment is higher than the appearance frequency in the other segments. I have it.

The present invention is premised on automatic exposure control (AE) of a video camera so that exposure is always properly performed and the average brightness of a video signal is controlled to be almost constant.

Here, the image signal is used as a signal including both analog video signal and digital video signal data.

Further, in the case of a movie video camera, the determination as to whether or not the backlight is to be taken is made by using the video signal of the previous field or the previous frame, and in the case of a still video camera, the preliminary shooting or the like. Is performed using the video signal obtained by.

Backlight photography means that the background is very bright and the main subject is dark, and not only so-called backlight photography, but also the case where the main subject is inside the room and through the window, such as photography in a room with a window. Including cases where the outside scenery is reflected.

According to the present invention, the image area corresponding to the section having the highest frequency among the sections of at least four stages is
It occupies the largest area on the shooting screen. In the case where the average brightness of the video signal is constant, if the appearance frequency of the brightness in the relatively bright one of the at least two stages divided into the dark one is higher than that of the other, It can be said that the image area occupying the largest area is in a dim state. It is highly possible that the image area occupying the largest area on the shooting screen contains the image of the main subject. When this widest image area appears dimly, it is highly possible that the main subject also appears dimly.

Therefore, in such a case, it is determined that the backlight photography requires backlight compensation.

Even if the area of the image area having the brightness included in the dim section is the largest in at least four steps of the above-mentioned brightness, the main subject may not exist in this image area. . For example, it is a case where a scene including a wall surface having a constant brightness with almost no change is photographed, the wall surface occupies a large area in the entire image, and the wall surface appears dim. The wall surface is not the main subject such as a person, and the main subject may be reflected in a bright part other than the wall surface. In that case, backlight compensation to make the wall brighter is unnecessary.

In order to cope with such a special case, in the preferred embodiment of the present invention, when it is determined that the area of the image area having the brightness included in the dim section is the largest, the backlight correction is performed by itself. It is not judged that the backlight is necessary, and the process proceeds further, and the frequency distribution of the brightness difference between the adjacent pixels in the image area corresponding to the relatively bright section among the two sections divided into the dark side is further obtained, and this brightness is calculated. If the difference frequency distribution is biased toward the larger brightness difference,
Alternatively, only when the frequency of the brightness difference equal to or more than the predetermined brightness difference is higher than the frequency of the other brightness difference, it is determined that the backlight shooting needs the backlight correction.

In the image area containing the image of the main subject, there is a change in luminance due to the existence of the image of the main subject, and whether the frequency distribution of the luminance difference between adjacent pixels is biased toward the larger luminance difference. Alternatively, the frequency of the brightness difference equal to or larger than the predetermined brightness difference is higher than the frequency of the other brightness differences. By examining the frequency distribution of the brightness difference between adjacent pixels, it is possible to identify whether the image area includes the image of the main subject or the above-described image area representing the wall surface. That is, it is possible to determine whether or not the main subject appears dimly. Then, only when the main subject appears in a dim light, it is determined that the backlight shooting requires backlight compensation.

The present invention provides a backlight correction method and apparatus for adjusting an image signal so that an image region including a relatively dark main subject has an appropriate brightness when it is determined that backlight correction is necessary. providing.

The backlight correction method according to the present invention performs a process of relatively increasing the level of an image signal representing a relatively dark image area when it is determined to be a backlight photography.

The backlight correction device according to the present invention is relatively dark based on the storage means for storing the image signal obtained by the image pickup and the distribution of the brightness of the image represented by the image signal stored in the storage means. Backlight determination means for determining backlight photography when the area is relatively wide compared to other areas, and a relatively bright area when backlight photography is determined by the backlight determination means. Compensation means for performing a process of relatively increasing the level of the image signal representing a relatively dark area as compared with the above.

As a concrete method, the video signal of the backlight correction is amplified while performing knee processing to increase the level of the video signal representing the relatively dark image area and the video signal representing the relatively bright image area. Not to be saturated, the image signal is divided into two, at least one image signal is amplified by an appropriate amplification factor, and the amplified image signal and the unamplified image signal are combined, There is a so-called inset combining method, in which an image signal representing a dark image area is amplified and the amplified image signal is replaced with an image signal representing a relatively dark area in the image signal obtained by photographing. .

By the backlight correction as described above, it is possible to obtain a photographed image in which the region including the main subject which occupies the widest area of the photographed image can be reproduced with appropriate brightness.

[0023]

1 and 2 show an embodiment of a backlight judgment method according to the present invention.

FIG. 1 shows a photographed image represented by a video signal obtained by image pickup. The area of this captured image is divided into about m × n = 100 areas (this division is
Needless to say, the number is not limited to 100), and the average luminance of each divided area (hereinafter referred to as a divided area) is obtained, and a histogram of the average luminance is created.

This histogram may be created by using the video signal of the previous field or the previous frame in the movie video camera and by using the video signal obtained by the preliminary shooting in the still video camera. .

An example of the created histogram of average brightness is shown in FIGS. 2 (a) to 2 (c) for three types of photographed images.
Is shown in. The horizontal axis represents the average brightness of the segmented area,
The vertical axis represents the frequency (the number of divided areas having average brightness in the same range). Considering the case where the video signal is converted to digital data by an 8-bit A / D converter,
The brightness value is expressed in 256 levels from 0 to 255.

The histograms of FIGS. 2 (a) to 2 (c) show the brightness (luminance) represented by the video signal as A on the dark side with the average luminance (luminance value = 124) of the entire photographed image as the boundary. (Brightness value range: 0 to 24) and B (25 to 124) in 2 stages, and brighter one in C (124 to 200) and D (201 to 255) in 2 stages. It The brightness is preferably a value after gamma correction.

Needless to say, the method of dividing the above-mentioned luminance range is arbitrary, but it is sufficient if the average luminance of the entire image is used as a boundary and is divided into at least two stages for bright and two stages for dark. .

The judgment of the backlight is performed as follows on the assumption that the average brightness in the entire photographed image is appropriately set by the automatic exposure control (AE).

(1) When the frequency of appearance of the divided areas having the average luminance included in the relatively bright luminance range C is the highest as in the histogram shown in FIG. This indicates that the occupied image area is captured brightly. The image area that occupies the largest area in the captured image often contains the image of the main subject, and it can be considered that the main subject is also captured brightly. Therefore, in this case, it is determined that the proper shooting is performed in normal light, and it is not determined that the backlight shooting is performed.

(2) As shown in FIG. 2B, when the frequency of the darkest luminance range A is highest, the image area occupying the largest area in the photographed image is photographed very dark. It is shown that. But in this case,
If the backlight correction described below is performed so that the image area that is captured darkly has an appropriate brightness, other bright image areas will be blown out in white, and the sacrifice of the backlight correction will increase. Therefore, in this case, it is not determined that the backlight photography requires backlight compensation.

(3) As shown in FIG. 2 (c), when the brightness in the relatively bright brightness range B of the two darker than the average brightness is the highest, it occupies the largest area in the photographed image. This indicates that the image area is dimly shot. By performing backlight correction so that an image area captured in a dim light becomes bright, the image of the main subject, which is often included in the widest image area, can be made an image with appropriate brightness. Moreover, since the image area that can be made to have proper brightness by this backlight correction is wide, even if the image quality of the image area of other small area is sacrificed to some extent, the adverse effect on the entire image is small. Therefore, when the histogram as shown in FIG. 2 (c) is obtained, it is determined that the backlight photography is performed.

When it is determined that the backlight shooting is performed, the backlight correction as described later is performed based on this determination.

Even if the histogram as shown in FIG. 2 (c), which has the highest frequency in the brightness range B, is obtained, it may be better not to determine that the backlight photographing is performed. For example, this is a case where the image area formed by the divided areas having the average brightness of the brightness range B includes only the image of the wide wall surface and does not include the main subject. In such a case, even if the backlight correction is performed, the image of the main subject cannot be made to have an appropriate brightness. On the contrary, the adverse effect on the other image area due to the backlight correction becomes conspicuous.

Therefore, preferably, when the frequency of the brightness range B is the highest in the histogram of the average brightness (FIG. 2 (c)), the image area of the brightness range B contains the image of the main subject. It is determined whether or not there is a backlight, and based on this determination result, a final determination is made as to whether or not the backlight shooting requires backlight compensation.

The determination as to whether or not the main subject is included in the image area consisting of the divided areas having the average brightness included in the brightness range B is based on the brightness difference histogram as shown in FIG. 3 as described below. Is done.

This brightness difference histogram represents a frequency distribution of brightness differences in one direction or two directions between adjacent pixels in a divided area having an average brightness belonging to the brightness range B. When the image of the main subject is included in the image area formed by the divided areas having the average brightness belonging to the brightness range B, the brightness change in the image area is large, and the image included in this image area is In the case of showing a flat wall surface, the luminance change is small.
It is possible to determine whether or not the image of the main subject is included in the image area formed by the divided areas having the average brightness belonging to the brightness range B, depending on the form of the brightness distribution of the brightness difference between the adjacent pixels.

Two typical methods of calculating the brightness difference necessary to create the brightness difference histogram will be described.

(1) Luminance difference calculation in one direction As shown in FIG. 4 (a), three adjacent one directions (for example, horizontal direction) in an image area constituted by divided areas having the average brightness of the brightness range B are used. Let the luminance of one pixel be a _j-1 , a _j, and a _{j + 1} . The brightness difference q _j for the central pixel is _calculated by the following equation.

[0040]

[Equation 1]

In Expression 1, n represents the number of pixels (here, n = 3) related to the brightness difference calculation.

By changing the value of j in one direction (horizontal direction), the average brightness of the brightness range B is further changed line by line in the direction (vertical direction) orthogonal to this one direction. luminance difference q _j by calculation of equation 1 with respect to all the pixels of an image formed area by dividing the area with
Is calculated.

(2) Luminance difference calculation in two directions As shown in FIG. 4 (b), nine pixels adjacent to each other in two directions included in the image area constituted by the divided areas having the average luminance of the luminance range B Brightness of a _{i-1, j-1 to} a
_{Let i + 1 and j + 1} . The brightness difference p _{i, j} for the central pixel is _calculated by the following equation.

[0044]

[Equation 2]

In Expression 2, n represents the number of pixels involved in the brightness difference calculation (here, n = 9).

With respect to all the pixels in the divided area having the average brightness included in the brightness range B, the calculation of the expression 2 is executed while changing i and j.

The value of the brightness difference q _j obtained by the above equation 1 or the value of the brightness difference p _{i, j} obtained by the above equation 2 is
When there is no change in brightness between adjacent pixels, it is zero, and when there is a change in brightness, the larger the change, the larger.

The luminance difference q _j or p _{i, j} thus obtained is small in this embodiment, depending on its magnitude,
It is divided into three stages of medium and large, and the number of pixels relating to the brightness difference belonging to the segment is counted for each segment. This count value becomes the frequency in each luminance difference section.

In the luminance difference histogram created in this way, as shown in FIG. 3, when the frequency of divisions with a large luminance difference is equal to or greater than a predetermined threshold value a, a divided area having average luminance belonging to the luminance range B is obtained. It means that there is a large change in brightness in the image area formed by, and it is considered that the image of the main subject is included in this image area. Therefore, in this case, it is determined that the backlight photography is performed.

However, in the brightness difference histogram, when the frequency of the sections with a large brightness difference does not exceed the predetermined threshold value a, the brightness change in the image area consisting of the divided areas having the average brightness of the brightness range B is not large. , It is considered that the image of the main subject is not included in this image area. Therefore, in this case, even if the frequency of the brightness range B is the largest in the histogram relating to the average brightness (FIG. 2 (c)), it is not judged that the backlight shooting requires backlight correction.

As described above, when it is determined that the backlight photographing is performed based on the histogram regarding the average luminance, preferably by further using the luminance difference histogram, the backlight compensation is performed by the method described below. .

FIG. 5 shows a part of the electronic still camera. In this electronic still camera, backlight shooting determination and backlight correction are performed.

The image pickup optical system includes an image pickup lens 11, a diaphragm 12, a shutter 13 and a solid-state electronic image pickup device (image sensor).
CCD 14 is included. The exposure control circuit 29 includes a CPU, and this circuit 29 determines the exposure amount based on the photometric signal obtained from the photometric sensor 27 and clears the charge in the diaphragm 12, the shutter 13 and the CCD 14, reads out the signal, etc. To control. The exposure control can be performed by adjusting at least one of the aperture value of the aperture 12 and the shutter speed of the shutter 13. The electronic shutter function of the CCD 14 may be used without providing the shutter 13. If necessary, the strobe device 28 may be driven to emit strobe light.

A video signal representing a subject image output from the CCD 14 by photographing is amplified by an amplifier 15 and then subjected to preprocessing such as γ correction in a preprocessing circuit 16. In the pre-shooting, the output video signal of the pre-processing circuit 16 is converted into digital image data by the A / D converter 18 and then temporarily stored in the frame memory 19. In the actual shooting, the output video signal of the preprocessing circuit 16 is input to the amplification / knee processing circuit 21.

In the preliminary photographing, the luminance component is extracted from the image data stored in the frame memory 19, and by using the luminance component image data, the backlight judging circuit 20 judges whether the backlight photographing is performed or not according to the above-mentioned method. Be done. The backlight determination circuit 20 preferably includes a CPU,
The PU divides the luminance component image data into a plurality of divided areas (FIG. 1), calculates average luminance for each divided area, and determines backlighting based on a histogram regarding average luminance (FIG. 2). The backlight determination process (FIG. 3) is performed in consideration of the brightness difference histogram in the pixel.
A control signal is created based on the result of determination by the backlight determination circuit 20 as to whether or not backlight shooting is performed, and this control signal is provided to the amplification / knee processing circuit 21.

The amplification / knee processing circuit 21 includes an amplification circuit and a knee circuit. The knee circuit works to lower the amplification factor of the amplifier circuit as the level of the input signal increases. The functions of these circuits can be realized by a hardware circuit for an analog input signal, a hardware circuit for a digital input signal, or a software process.

FIG. 6 shows the relationship between the brightness of a photographed image and the level of a video signal representing this image, with the level and brightness of the video signal normalized between 0 and 100%. The characteristics of the video signal output from the preprocessing circuit 16 may be considered.

FIG. 7 shows that when a video signal having the characteristics shown in FIG. 6 is input to the amplification / knee processing circuit 21, amplification / knee processing is performed.
The characteristics of the video signal obtained from the knee processing circuit 21 are shown. As can be seen from the solid curve indicated by V1 in this graph, the video signal representing the dark portion of the image is considerably amplified and its level is increased. The level of the video signal representing the bright portion of the image remains almost unchanged. Broken line V
2 shows the case where the input video signal is simply amplified and the knee process is not applied. If the input video signal is simply amplified, the level of the video signal representing a bright portion becomes too high, and a whiteout phenomenon occurs in the reproduced image. By the function of knee treatment,
Since the amplification factor of the video signal representing the bright portion can be suppressed to be relatively small, the characteristic shown by V1 can be obtained.

The video signal obtained by the main photographing after the preliminary photographing and output from the preprocessing circuit 16 is input to the amplification / knee processing circuit 21. The circuit 21 performs amplification and knee processing on the input video signal when the control signal indicating that the backlight correction is to be performed is given from the backlight determination circuit 20 to generate a video signal having the characteristics shown in FIG. Output. When the control signal indicating that the backlight correction should be performed is not given, the amplification / knee processing circuit 21 outputs the input video signal as it is without any processing. amplification/
It is sufficient to perform knee processing on at least the luminance component of the input video signal.

The output signal of the amplification / knee processing circuit 21 is subjected to necessary signal processing and output to the outside, or converted into digital image data, compressed and stored in a memory card.

FIG. 8 shows another embodiment. In this embodiment, backlight compensation is performed by combining by weighted addition. In FIG. 8, the same parts as those shown in FIG.

On the other hand, the video signal output from the preprocessing circuit 16 is converted into digital image data by the A / D converter 18A and applied to the frame memory 19, and is also applied to the synthesizing circuit 23 as the image data A. On the other hand, it is amplified by the amplifier circuit 17 (for example, 12 dB) and the A / D converter
It is converted into digital image data B in 18B and is synthesized by the synthesis circuit 23
Given to.

As described above, the backlight judgment circuit 20 judges whether or not the backlight is photographed based on the image data obtained by the preliminary photographing, and the control signal based on the backlight photographing judgment result is sent to the synthesizing circuit 23. Given.

Some examples of the configuration of the synthesis circuit 23 are shown in FIGS. 9 and 10.

In FIG. 9, the image data A is multiplied by (1−α) in the coefficient unit 63 using an appropriate coefficient α (α <1). The image data B is multiplied by α by the coefficient unit 64. The output image data of these coefficient units 63 and 64 is added by the adder 65.
Is added to form image data E. The combined image data E is subjected to vertical contour enhancement processing in the edge forcing circuit 66. The level of image data E after composition corresponds to the brightness
Shown in 11. At the output E, the image data is only the image data B up to a certain level (data that is not multiplied by α)
Is adopted.

In FIG. 10, the coefficient α changes according to the level of the image data A (subject brightness) as shown in FIG. That is, the coefficient α is large in a portion where the level of the image data A is low (the luminance is small), and the coefficient α is small as the level of the image data A is high (the luminance is large). Such a coefficient α is stored in the look-up table (LUT) 67 in advance. The address of the LUT 67 is designated by the image data A, and the data representing the corresponding coefficient α is read. The coefficient α read from the LUT 67 is given to the coefficient units 63 and 64, respectively. Therefore, the combined image data F are smoothly connected as shown in FIG. The edge enhancement circuit is not particularly shown in FIG.

The output image data E of such a synthesis circuit 23
Alternatively, F is subjected to knee processing or the like in the signal processing circuit 24 as needed. The edge enhancement circuit 66 may be included in the signal processing circuit 62.

It goes without saying that the synthesizing circuit by weighted addition shown in FIG. 8 can be realized in an analog manner.

The synthesizing circuit 23 performs the above-mentioned weighted addition synthesizing process in response to the control signal indicating that the backlight should be corrected from the backlight determining circuit 20 when the main photographing is performed, and other If the image data A is (1-α)
Pass it through without doubling.

The image data output from the synthesis circuit 23 is
It is converted into an analog video signal by the D / A converter 25 and output. This analog video signal is given to a display device such as a CRT. The video signal can be FM-modulated and recorded on a magnetic recording medium such as a floppy disk or a magnetic tape. Alternatively, the output image data of the synthesizing circuit 23 is separated (Y / C separated) into luminance data and color data by the image data processing circuit 26, and the data is compressed.
It may be encoded and then recorded in the memory card.

Backlight correction can also be performed by a process of fitting and combining image data or video signals. The inset synthesizing process creates two identical first and second image signals from the image signal obtained by photographing, and at least the second image signal is regarded as a relatively bright area of the image represented by the image signal. Amplify according to the difference in brightness from the relatively dark area, find the boundary between the relatively bright area and the relatively dark area of the above image, and relatively brightly divided by the found boundary The first image signal is applied to the area, and the second image signal is applied to the relatively dark area.
The composite image signal is created by using each of the image signals. An image reproduced based on this composite image signal is expressed with appropriate brightness in both a relatively bright area and a dark area, and the brightness is clear, and the image is easy to see and excellent. Such an embedded synthesizer is the applicant's prior application (for example, Japanese Patent Application No. 4-2439933).
It is described in.

[Brief description of drawings]

FIG. 1 is a diagram showing captured images divided for creating a histogram.

2A, 2B and 2C are graphs showing histograms of average luminance.

3A shows a pixel arrangement when calculating a luminance difference in one direction, and FIG. 3B shows a pixel arrangement when calculating a luminance difference in two directions.

FIG. 4 is a graph showing a luminance difference histogram.

FIG. 5 is a block diagram showing a configuration of an electronic still camera that performs backlight determination and backlight compensation according to the present invention.

FIG. 6 is a graph showing the relationship between the relative brightness of an image and the level of a video signal.

FIG. 7 is a graph showing a relationship between relative brightness of an image after backlight correction and a level of an output video signal.

FIG. 8 is a block diagram showing another example of an electronic still camera.

FIG. 9 is a block diagram illustrating a configuration example of a synthesis circuit.

FIG. 10 is a block diagram showing another configuration example of a synthesizing circuit.

11 is a graph showing the level of output image data of the synthesizing circuit shown in FIG.

12 is a graph showing coefficients used in the synthesizing circuit shown in FIG.

13 is a graph showing the level of output image data of the synthesizing circuit shown in FIG.

[Explanation of symbols]

 17 Amplification circuit 18, 18A, 18B A / D converter 19 Frame memory 20 Backlight judgment circuit 21 Amplification / Knee processing circuit 23 Compositing circuit

Claims (6)

[Claims] 1. A range of brightness represented by an image signal obtained by image pickup is divided into at least two steps in total, that is, at least two steps for the bright side and two steps for the dark side with an average brightness as a boundary. A backlight determination method for obtaining the appearance frequency of brightness in each stage, and determining the backlight photography when the appearance frequency in the relatively bright segment of the two stages divided into the dark one is higher than the appearance frequency in other segments . 2. A frequency distribution of luminance differences between adjacent pixels in an image region corresponding to a relatively bright segment of the two stages divided into dark ones is further obtained, and the frequency distribution of the luminance differences has a large luminance difference. The backlight determination method according to claim 1, wherein the backlight determination is performed only when it is biased toward one side or when the frequency of the brightness difference equal to or more than a predetermined brightness difference is higher than the frequency of other brightness differences. 3. When the backlight determination method according to claim 1 or 2 determines that the backlight shooting is performed, the level of an image signal representing a relatively dark image area is compared with a relatively bright image area. Backlight compensation method that performs relatively high processing. 4. An image pickup means for outputting an image signal representing a subject, an image storage means for storing an image signal output from the image pickup means, and a range of brightness in an image stored in the image storage means are averaged. At least 4 levels of lightness and 2 levels of darkness are classified into a total of at least 4 levels, and the frequency of brightness at each level is calculated. A backlight judgment device comprising: a backlight judgment unit that judges backlight photography when the appearance frequency in a bright section is higher than the appearance frequencies in other sections. 5. The backlight determining means further obtains a frequency distribution of luminance differences between adjacent pixels in an image region corresponding to a relatively bright segment among the two stages segmented in the dark side,
The backlight distribution is determined only when the frequency distribution of the brightness difference is biased toward the larger brightness difference or when the frequency of the brightness difference of a predetermined brightness difference or more is larger than the frequency of other brightness differences. The backlight determination device according to claim 4. 6. A storage means for storing an image signal obtained by image pickup, and the size of a relatively dark region is different based on a distribution of brightness of an image represented by the image signal stored in the storage means. The backlight determination means for determining the backlight shooting when the area is relatively wide compared to the area of the area, and when the backlight determination is determined by the backlight determination means, the backlight is relatively compared with the bright area. A backlight correction device comprising: a correction unit that performs a process of relatively increasing the level of an image signal that represents a dark area.